Water and Heat Transport in the Desert Soil and Atmospheric Boundary Layer in Western China

Abstract

In order to understand the exchange and transferprocesses of water and energy in the desert soil andthe atmospheric boundary layer (ABL), we have developeda coupled model, in which a desert soil modelincluding water movement of both liquid and vapourphase, and an ABL model based on a non-local transilientturbulence closure scheme, are coupled together. Withthis model, the evolution of potential temperature andspecific humidity, the distribution of net radiationamong sensible, latent and soil heat fluxes, and thewater and heat flux profiles both in the soil and ABLhave been simulated. The HEIFE (HEIhe River Basin FieldExperiment) observational data are used to calibrate calculation of the water and heat flux both in thesoil and the ABL. The sensible and latent heatfluxes warm and moisten the bottom grid box (100m) of theABL. In this way the ABL model and the desert soil model are coupled together. The simulated results show that when the flux of watervapour in the soil is neglected, the evaporation rateand the flux profiles of specific humidity in the ABLshow great changes, hence the importance of watervapour movement in the desert soil for the calculationof specific humidity in the ABL. In the upper 5cm of thesoil, which is called an active layer, water andheat transport are more effective than in the substrate(soil below 5 cm).